Actuators are in wide spread use to actuate other implements or devices. The applications of actuators are virtually limitless and the size, shape, etc. of the actuator as well as the device actuated is relatively unconstrained. Hydraulic cylinders are one commonly used form of actuators. Such actuators include a cylinder and an internal piston which actuates an external device. In many actuator applications, there is a need for greater control of the movement of the device imparted by the actuator. One example of this need is in the equipment arena where hydraulic cylinders are used as actuators to control the movement of a mechanical device, such as the bucket or claw on construction equipment.
There are, in use today, various types of piston position sensors that are used to accurately sense the position of a piston within a hydraulic cylinder. The operation of such hydraulic cylinders, therefore, depends upon a position sensor to automatically and accurately determine the location of a piston with the hydraulic cylinder, and correspondingly, the position of the particular implement that is being controlled by that hydraulic cylinder. One of such sensors and its use and construction is shown and described in U.S. Pat. No. 6,234,061 entitled “Precision Sensor for a Hydraulic Cylinder,” and the disclosures of which is hereby incorporated by reference. That particular sensor is, therefore, one that is positioned within the interior of the hydraulic cylinder proximate the closed end of the cylinder, that is, the end opposite the working end where the piston rod extends to be affixed to the equipment to be moved.
In the construction and assembly of hydraulic cylinders, the manufacture of such hydraulic cylinders is an established, well-defined process. It is desirable not to disrupt that process by adding some additional complexity to the manufacturing techniques, that is, the less changes that are required in the current manufacturing practices, the better the acceptance of the sensor.
In the normal manufacturing practices of assembling a hydraulic cylinder, the final assembly consists of bringing together two major subassemblies, the “tube assembly” and the “piston rod” assembly. The tube assembly consists mainly of the cylinder tube with the back cap attached thereto and the other end is open to receive the piston rod assembly. The piston rod assembly, on the other hand, consists of the piston rod, the head and the piston. As such, in the final assembly, the piston rod assembly is inserted into the tube assembly similar to loading a cannon such that the piston is inserted into the open end of the cylinder tube and is pushed all the way back to the closed end of the cylinder tube. When so inserted the head is positioned at the open end of the cylinder tube and secured thereto, either by means of a threaded connection by threads formed internal of the cylinder tube and threads formed external to the head, or by means of bolts that are threaded into a mating flange welded to the open end of the cylinder tube. In either case, once the head has been secured to the open end of the cylinder tube, the cylinder assembly is complete.
Accordingly, it would be advantageous to provide a system or procedural steps in the manufacture of a hydraulic cylinder to be able to install a sensor in the closed end of a cylinder tube, and secure the sensor at that location while minimizing disruptions and changes to current manufacturing practices for the construction and assembly of such hydraulic cylinders.